* modules/string (Makefile.am): New indicator.
* m4/string_h.m4 (gl_HEADER_STRING_H_DEFAULTS): Set it.
* lib/string.in.h (rawmemchr): Declare when appropriate.
* modules/rawmemchr: New file.
* m4/rawmemchr.m4: Likewise.
* lib/rawmemchr.c: Likewise.
* modules/rawmemchr-tests: Likewise.
* tests/test-rawmemchr.c: Likewise.
* doc/glibc-functions/rawmemchr.texi (rawmemchr): Document
module.
* modules/strchrnul (Depends-on): Add rawmemchr.
* lib/strchrnul.c (strchrnul): Optimize a corner case.
Signed-off-by: Eric Blake <ebb9@byu.net>
2008-04-28 Eric Blake <ebb9@byu.net>
+ Add rawmemchr module, matching glibc.
+ * modules/string (Makefile.am): New indicator.
+ * m4/string_h.m4 (gl_HEADER_STRING_H_DEFAULTS): Set it.
+ * lib/string.in.h (rawmemchr): Declare when appropriate.
+ * modules/rawmemchr: New file.
+ * m4/rawmemchr.m4: Likewise.
+ * lib/rawmemchr.c: Likewise.
+ * modules/rawmemchr-tests: Likewise.
+ * tests/test-rawmemchr.c: Likewise.
+ * doc/glibc-functions/rawmemchr.texi (rawmemchr): Document
+ module.
+ * modules/strchrnul (Depends-on): Add rawmemchr.
+ * lib/strchrnul.c (strchrnul): Optimize a corner case.
+
Whitespace cleanup.
* tests/test-strchrnul.c: Reindent.
* lib/strchrnul.c: Likewise.
@subsection @code{rawmemchr}
@findex rawmemchr
-Gnulib module: ---
+Gnulib module: rawmemchr
Portability problems fixed by Gnulib:
@itemize
+@item
+This function is missing on all non-glibc platforms:
+MacOS X 10.3, FreeBSD 6.0, NetBSD 3.0, OpenBSD 3.8, AIX 5.1, HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 10, Cygwin, mingw, Interix 3.5, BeOS.
@end itemize
Portability problems not fixed by Gnulib:
@itemize
-@item
-This function is missing on all non-glibc platforms:
-MacOS X 10.3, FreeBSD 6.0, NetBSD 3.0, OpenBSD 3.8, AIX 5.1, HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 10, Cygwin, mingw, Interix 3.5, BeOS.
@end itemize
--- /dev/null
+/* Searching in a string.
+ Copyright (C) 2008 Free Software Foundation, Inc.
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#include <config.h>
+
+/* Specification. */
+#include <string.h>
+
+/* Find the first occurrence of C in S. */
+void *
+rawmemchr (const void *s, int c_in)
+{
+ /* On 32-bit hardware, choosing longword to be a 32-bit unsigned
+ long instead of a 64-bit uintmax_t tends to give better
+ performance. On 64-bit hardware, unsigned long is generally 64
+ bits already. Change this typedef to experiment with
+ performance. */
+ typedef unsigned long int longword;
+
+ const unsigned char *char_ptr;
+ const longword *longword_ptr;
+ longword repeated_one;
+ longword repeated_c;
+ unsigned char c;
+
+ c = (unsigned char) c_in;
+
+ /* Handle the first few bytes by reading one byte at a time.
+ Do this until CHAR_PTR is aligned on a longword boundary. */
+ for (char_ptr = (const unsigned char *) s;
+ (size_t) char_ptr % sizeof (longword) != 0;
+ ++char_ptr)
+ if (*char_ptr == c)
+ return (void *) char_ptr;
+
+ longword_ptr = (const longword *) char_ptr;
+
+ /* All these elucidatory comments refer to 4-byte longwords,
+ but the theory applies equally well to any size longwords. */
+
+ /* Compute auxiliary longword values:
+ repeated_one is a value which has a 1 in every byte.
+ repeated_c has c in every byte. */
+ repeated_one = 0x01010101;
+ repeated_c = c | (c << 8);
+ repeated_c |= repeated_c << 16;
+ if (0xffffffffU < (longword) -1)
+ {
+ repeated_one |= repeated_one << 31 << 1;
+ repeated_c |= repeated_c << 31 << 1;
+ if (8 < sizeof (longword))
+ {
+ size_t i;
+
+ for (i = 64; i < sizeof (longword) * 8; i *= 2)
+ {
+ repeated_one |= repeated_one << i;
+ repeated_c |= repeated_c << i;
+ }
+ }
+ }
+
+ /* Instead of the traditional loop which tests each byte, we will
+ test a longword at a time. The tricky part is testing if *any of
+ the four* bytes in the longword in question are equal to NUL or
+ c. We first use an xor with repeated_c. This reduces the task
+ to testing whether *any of the four* bytes in longword1 is zero.
+
+ We compute tmp =
+ ((longword1 - repeated_one) & ~longword1) & (repeated_one << 7).
+ That is, we perform the following operations:
+ 1. Subtract repeated_one.
+ 2. & ~longword1.
+ 3. & a mask consisting of 0x80 in every byte.
+ Consider what happens in each byte:
+ - If a byte of longword1 is zero, step 1 and 2 transform it into 0xff,
+ and step 3 transforms it into 0x80. A carry can also be propagated
+ to more significant bytes.
+ - If a byte of longword1 is nonzero, let its lowest 1 bit be at
+ position k (0 <= k <= 7); so the lowest k bits are 0. After step 1,
+ the byte ends in a single bit of value 0 and k bits of value 1.
+ After step 2, the result is just k bits of value 1: 2^k - 1. After
+ step 3, the result is 0. And no carry is produced.
+ So, if longword1 has only non-zero bytes, tmp is zero.
+ Whereas if longword1 has a zero byte, call j the position of the least
+ significant zero byte. Then the result has a zero at positions 0, ...,
+ j-1 and a 0x80 at position j. We cannot predict the result at the more
+ significant bytes (positions j+1..3), but it does not matter since we
+ already have a non-zero bit at position 8*j+7.
+
+ The test whether any byte in longword1 is zero is equivalent
+ to testing whether tmp is nonzero.
+
+ This test can read beyond the end of a string, depending on where
+ C_IN is encountered. However, this is considered safe since the
+ initialization phase ensured that the read will be aligned,
+ therefore, the read will not cross page boundaries and will not
+ cause a fault. */
+
+ while (1)
+ {
+ longword longword1 = *longword_ptr ^ repeated_c;
+
+ if ((((longword1 - repeated_one) & ~longword1)
+ & (repeated_one << 7)) != 0)
+ break;
+ longword_ptr++;
+ }
+
+ char_ptr = (const unsigned char *) longword_ptr;
+
+ /* At this point, we know that one of the sizeof (longword) bytes
+ starting at char_ptr is == c. On little-endian machines, we
+ could determine the first such byte without any further memory
+ accesses, just by looking at the tmp result from the last loop
+ iteration. But this does not work on big-endian machines.
+ Choose code that works in both cases. */
+
+ char_ptr = (unsigned char *) longword_ptr;
+ while (*char_ptr != c)
+ char_ptr++;
+ return (void *) char_ptr;
+}
unsigned char c;
c = (unsigned char) c_in;
+ if (!c)
+ return rawmemchr (s, 0);
/* Handle the first few bytes by reading one byte at a time.
Do this until CHAR_PTR is aligned on a longword boundary. */
memrchr (a, b, c))
#endif
+/* Find the first occurrence of C in S. More efficient than
+ memchr(S,C,N), at the expense of undefined behavior if C does not
+ occur within N bytes. */
+#if @GNULIB_RAWMEMCHR@
+# if ! @HAVE_RAWMEMCHR@
+extern void *rawmemchr (void const *__s, int __c_in)
+ __attribute__ ((__pure__));
+# endif
+#elif defined GNULIB_POSIXCHECK
+# undef rawmemchr
+# define rawmemchr(a,b) \
+ (GL_LINK_WARNING ("rawmemchr is unportable - " \
+ "use gnulib module rawmemchr for portability"), \
+ rawmemchr (a, b))
+#endif
+
/* Copy SRC to DST, returning the address of the terminating '\0' in DST. */
#if @GNULIB_STPCPY@
# if ! @HAVE_STPCPY@
--- /dev/null
+# rawmemchr.m4 serial 1
+dnl Copyright (C) 2003, 2007, 2008 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_FUNC_RAWMEMCHR],
+[
+ dnl Persuade glibc <string.h> to declare rawmemchr().
+ AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+
+ AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+ AC_REPLACE_FUNCS([rawmemchr])
+ if test $ac_cv_func_rawmemchr = no; then
+ HAVE_RAWMEMCHR=0
+ gl_PREREQ_RAWMEMCHR
+ fi
+])
+
+# Prerequisites of lib/strchrnul.c.
+AC_DEFUN([gl_PREREQ_RAWMEMCHR], [:])
GNULIB_MEMMEM=0; AC_SUBST([GNULIB_MEMMEM])
GNULIB_MEMPCPY=0; AC_SUBST([GNULIB_MEMPCPY])
GNULIB_MEMRCHR=0; AC_SUBST([GNULIB_MEMRCHR])
+ GNULIB_RAWMEMCHR=0; AC_SUBST([GNULIB_RAWMEMCHR])
GNULIB_STPCPY=0; AC_SUBST([GNULIB_STPCPY])
GNULIB_STPNCPY=0; AC_SUBST([GNULIB_STPNCPY])
GNULIB_STRCHRNUL=0; AC_SUBST([GNULIB_STRCHRNUL])
HAVE_DECL_MEMMEM=1; AC_SUBST([HAVE_DECL_MEMMEM])
HAVE_MEMPCPY=1; AC_SUBST([HAVE_MEMPCPY])
HAVE_DECL_MEMRCHR=1; AC_SUBST([HAVE_DECL_MEMRCHR])
+ HAVE_RAWMEMCHR=1; AC_SUBST([HAVE_RAWMEMCHR])
HAVE_STPCPY=1; AC_SUBST([HAVE_STPCPY])
HAVE_STPNCPY=1; AC_SUBST([HAVE_STPNCPY])
HAVE_STRCHRNUL=1; AC_SUBST([HAVE_STRCHRNUL])
--- /dev/null
+Description:
+rawmemchr() function: Find the first occurrence of C in S.
+
+Files:
+lib/rawmemchr.c
+m4/rawmemchr.m4
+
+Depends-on:
+extensions
+string
+
+configure.ac:
+gl_FUNC_RAWMEMCHR
+gl_STRING_MODULE_INDICATOR([rawmemchr])
+
+Makefile.am:
+
+Include:
+<string.h>
+
+License:
+LGPL
+
+Maintainer:
+FSF
--- /dev/null
+Files:
+tests/test-rawmemchr.c
+
+Depends-on:
+
+configure.ac:
+
+Makefile.am:
+TESTS += test-rawmemchr
+check_PROGRAMS += test-rawmemchr
Depends-on:
extensions
string
+rawmemchr
configure.ac:
gl_FUNC_STRCHRNUL
-e 's|@''GNULIB_MEMMEM''@|$(GNULIB_MEMMEM)|g' \
-e 's|@''GNULIB_MEMPCPY''@|$(GNULIB_MEMPCPY)|g' \
-e 's|@''GNULIB_MEMRCHR''@|$(GNULIB_MEMRCHR)|g' \
+ -e 's|@''GNULIB_RAWMEMCHR''@|$(GNULIB_RAWMEMCHR)|g' \
-e 's|@''GNULIB_STPCPY''@|$(GNULIB_STPCPY)|g' \
-e 's|@''GNULIB_STPNCPY''@|$(GNULIB_STPNCPY)|g' \
-e 's|@''GNULIB_STRCHRNUL''@|$(GNULIB_STRCHRNUL)|g' \
-e 's|@''HAVE_DECL_MEMMEM''@|$(HAVE_DECL_MEMMEM)|g' \
-e 's|@''HAVE_MEMPCPY''@|$(HAVE_MEMPCPY)|g' \
-e 's|@''HAVE_DECL_MEMRCHR''@|$(HAVE_DECL_MEMRCHR)|g' \
+ -e 's|@''HAVE_RAWMEMCHR''@|$(HAVE_RAWMEMCHR)|g' \
-e 's|@''HAVE_STPCPY''@|$(HAVE_STPCPY)|g' \
-e 's|@''HAVE_STPNCPY''@|$(HAVE_STPNCPY)|g' \
-e 's|@''HAVE_STRCHRNUL''@|$(HAVE_STRCHRNUL)|g' \
--- /dev/null
+/*
+ * Copyright (C) 2008 Free Software Foundation
+ * Written by Eric Blake and Bruno Haible
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#include <config.h>
+
+#include <string.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#define ASSERT(expr) \
+ do \
+ { \
+ if (!(expr)) \
+ { \
+ fprintf (stderr, "%s:%d: assertion failed\n", __FILE__, __LINE__); \
+ fflush (stderr); \
+ abort (); \
+ } \
+ } \
+ while (0)
+
+/* Calculating void * + int is not portable, so this wrapper converts
+ to char * to make the tests easier to write. */
+#define RAWMEMCHR (char *) rawmemchr
+
+int
+main ()
+{
+ size_t n = 0x100000;
+ char *input = malloc (n + 1);
+ ASSERT (input);
+
+ input[0] = 'a';
+ input[1] = 'b';
+ memset (input + 2, 'c', 1024);
+ memset (input + 1026, 'd', n - 1028);
+ input[n - 2] = 'e';
+ input[n - 1] = 'a';
+ input[n] = '\0';
+
+ /* Basic behavior tests. */
+ ASSERT (RAWMEMCHR (input, 'a') == input);
+ ASSERT (RAWMEMCHR (input, 'b') == input + 1);
+ ASSERT (RAWMEMCHR (input, 'c') == input + 2);
+ ASSERT (RAWMEMCHR (input, 'd') == input + 1026);
+
+ ASSERT (RAWMEMCHR (input + 1, 'a') == input + n - 1);
+ ASSERT (RAWMEMCHR (input + 1, 'e') == input + n - 2);
+
+ ASSERT (RAWMEMCHR (input, '\0') == input + n);
+
+ /* Alignment tests. */
+ {
+ int i, j;
+ for (i = 0; i < 32; i++)
+ {
+ for (j = 0; j < 256; j++)
+ input[i + j] = j;
+ for (j = 0; j < 256; j++)
+ {
+ ASSERT (RAWMEMCHR (input + i, j) == input + i + j);
+ }
+ }
+ }
+
+ free (input);
+
+ return 0;
+}
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